Flush toilets are in widespread use throughout the world for disposing of both fluid and solid waste. The standard construction for such toilets is to provide a holding tank for the water to be used in a flush,from which the water is fully discharged each time the toilet is flushed. The amount of water in the holding tank is selected to be sufficient to dispose of solid waste deposited into the toilet bowl. This requires a relatively large quantity of water. For disposal of fluid waste only, however, utilizing the full contents of the holding tank is wasteful, since fluid wastes can be disposed of with a much lower volume of water.
In many areas of the world, such as in the Southwestern United States, water is in short supply. Efforts to conserve water include efforts to reduce the amount of water consumed in a flush toilet each time the flush mechanism is operated. Some of these efforts simply employ devices for limiting the amount of water in the tank; so that a lower volume of water is used each time the toilet is flushed. Approaches of this nature, however, frequently result in unsatisfactory disposal of solid waste, since often it is necessary to flush such a low water volume toilet more than once in order to dispose of solid wastes. This defeats the purpose of the low volume. Such toilets generally do not have any problem in disposing of purely liquid waste.
In efforts to alleviate the problems associated with simply reducing the water level every time a toilet is flushed, dual flush toilet devices have been designed. These toilets are selectively operated to use the full volume water available for solid waste disposal, and to use a lesser volume of water for liquid waste disposal.
Two United States patents, Pozo U.S. Pat. No. 4,172,299 and Navarrette U.S. Pat. No. 5,175,893, disclose dual flush mechanisms. In the devices of both of these patents, flush valves are located at different heights on a discharge pipe inside the toilet tank. One of these valves is located near the bottom of the holding tank; and the other valve is located at an intermediate position above the other or first of the valves. When a full flush is desired, the flapper valve located at the lowermost position is operated to discharge the full volume of water into the toilet bowl for effecting flushing of solid waste. When a partial flush, for disposing of fluid waste only, is desired, the upper flapper valve is opened. Thus, less water is required to effect a flush, since the upper valve closes before the water level in the tank drops to the bottom of the tank. The pressure available for effecting a partial flush, however, is less than the pressure available for the full flush because of the location of the partial flush valve at a higher position within the tank. As a consequence, the flushing action which takes place in the toilet bowl is not as vigorous for a partial flush as it is for a full flush because of this reduced pressure.
Another approach to providing reduced volume water flushes in a toilet tank is disclosed in the U.S. patent to Kern U.S. Pat. No. 3,820,170. This patent is directed to a modification of a standard toilet tank to permit it to provide only reduced water flushes. This is not a dual flush device. The device of this patent utilizes a smaller container or barrier in the tank around the discharge pipe; so that when the flush mechanism is operated, only the water which is above the top of this container or barrier, and then located within the barrier, is used to effect the flush. This leaves the remainder of the water in the tank surrounding the barrier unused. This patent is directed to an installation which is to be made to an existing toilet tank to reduce the amount of water available for a flush operation.
An after-market installation for effecting a dual flush operation is disclosed in the U.S. patent to Gruenhagen U.S. Pat. No. 3,842,444. This patent discloses a closed compartment which is placed in the toilet over the exhaust or discharge pipe in the bottom of the holding tank. The compartment then surrounds the valve which normally is associated with the discharge pipe. The compartment is hinged at one side, and is magnetically held in place at the other side. Thus, some very specific installation requirements must be made in order to place this device in an existing toilet holding tank. When a partial flush is desired, operation of a lever lifts the stopper from the exhaust pipe in the chamber. The water in the chamber is used to effect the partial flush. Water in the remainder of the tank surrounding the chamber is not used for such a low volume flush operation. When a full volume flush is desired, the valve in the chamber first is lifted; then further operation of the handle or operating lever lifts the entire inner tank up on the edge opposite the hinge to permit the water to flow under that edge and through the discharge or exhaust pipe. Thus, the entire contents of the tank are emptied for such a full flush. At the end of the full flush, the tank drops back into place and is held against the bottom of the toilet holding tank by the magnet. The flapper valve within the inner tank also closes in a normal manner. This is a relatively complex device.
The United States patent to Zaruba U.S. Pat. No. 5,111,537 discloses several versions of a dual flush toilet. Some of these versions include a pair of flapper valves located at different heights within the tank to effect the flushing, but in the manner described previously in conjunction with the Pozo and Navarrette patents. FIG. 9 of this patent, however, shows a dual flush version which uses an auxiliary inner tank surrounding the exhaust pipe or discharge pipe in the holding tank. This auxiliary inner tank has a valve located in the bottom of it, much like the one in the Gruenhagen patent discussed above. In addition, there is a flapper valve located in the side of this tank. For a partial flush, the original or inner valve is opened and only the water in the inner tank is discharged. When a full flush is desired, the two valves both are opened to permit water in the tank to flow from the main tank through the opening in the side of the auxiliary tank, and then out through the discharge pipe in the bottom of the holding tank.
The U.S. patent to Wilhelm U.S. Pat. No. 3,719,958 is a custom or factory made toilet tank for effecting a dual flush operation. This is not a device which may be added to a standard toilet holding tank originally designed for a single flush operation. In the device of Wilhelm, two different discharge openings are provided in the bottom of the tank. A separate standpipe is formed around one of these openings to effect a partial flush, where only the water within this standpipe is discharged. For a full flush, both of the stoppers or valves are raised; so that the water within the standpipe as well as the water within the main tank is used to effect the flush.
It is desirable to provide an improved dual flush control system for releasing different amounts of water from the holding tank of a toilet into a discharge pipe opening in the bottom of the holding tank, which overcomes the disadvantages of the prior art, which is simple in construction, easy to install and simple to operate.